For well over 300 years meteorological instruments have been used to measure the direction and velocity of the winds. These instruments contributed substantially to the location of sites for the extensive use of mechanical wind power during the early history of mechanized industry, and most particularly in the late 19th Century. With the development of the steam engine, and later electrical power that was readily available in most remote locations of the country, wind power became virtually a lost science.
Only within the past decade has there been a renewed and active interest in using the energy from the winds for the generation of electrical, mechanical and thermal power. Typical wind turbine generators now exist for converting wind energy into each primary power type, but no know prior art system exists that is designed specifically as a complete system for the direct metering and recording of these energy and power functions
The power level of the wind is proportional to the density of the air mass times the cube of the wind velocity. Energy is this power function multiplied by the time of production; times the wind cross section are intercepted by, and aerodynamic characteristics of, the turbine blades; times the Betz Law efficiency constant (if applicable); times the total power conversion efficiency of the generator and mechanical linkages. Energy may be measured in equivalent units of kilowatt hours, horsepower hours or British thermal units. Because of recent advances in the related technologies it is now possible to obtain a major percentage of the electrical power required by a household from a properly sited wind turbine electric generator and it is further estimated that by the year 2000 over 10% of the national energy requirement may be derived from the wind by generators located at or near the point of use.
References may be made to meteorological anemometers or other wind direction and velocity meters, of many configurations, which have remained functionally unchanged but continued to be technically advanced by an increasing sophistication of modern technology. They have for example become smaller, more accurate and reliable, and use new electrical and electronic components to generally improve their basic performance but at increasing cost. Computing systems have also been advanced at a remarkable rate so that now a small programable micro-processor that can be held in the palm of the hand will perform complex mathematical computations automatically and will operate for many hours on a small battery. Similarly, sophisticated recording instruments of many kinds have been developed that are small, battery powered, portable and accurate, and can operate in moderately severe field environments for many hours to produce a permanent record of data of all kinds, digital and analogue, including wind characteristic data.
From the need and desire to obtain new measurements and precise data for the computation of wind energy and power potentials of specific sites, each of these independent and readily available devices have been generally contrived into various prior art systems for the metering and continuous recording of wind velocity and direction data, wind "depth" or duration-intensity measurement and to approximately simulate in digital computer circuits the field performance of specific wind turbine electrical generators. However, these prior art systems are typically very expensive, complex, are not self-powered so must have their batteries replaced frequently or are confined in their utility by operating only on commercial or other available electrical power, and are a serious maintenance problem due to poor system reliability and high levels of technical sophistication. Expensive laboratory instruments also are needed to maintain and calibrate these systems. This trend in development has been abetted by the fact that these general purpose devices and instruments are readily available but have not been designed specifically for their final intended end use; i.e. as a simple completely integrated wind energy metering and recording system. The various recorders now in use must also be serviced frequently with replacement components needed to renew their function, may not function in extreme weather conditions; and the data collected is often so frequent and extensive that it must be post-processed on large scale computers which adds appreciably to the expense and technical complexity of such measurements. The technical skill generally required to properly install, operate, maintain and utilize the data from these prior art systems are generally those of highly trained engineers and scientists experienced in electronics, digital data processing and atmospheric sciences. Also, because of their nature and expense, these prior art systems are an attractive object that may be sought out by vandals for pilferage or destruction.
To minimize the equipment complexities and associated technical requirements and costs in prior art systems, compromises have been made in the data quality or frequency of measurement. As a few examples: average hourly to daily wind velocity or integrated wind flow distances or "depth" have been recorded, which are technically and mathematically incorrect for wind energy computations; and the use of continuous on-line instrument computations has been eliminated in favor of complex off-line computer processing of only periodic wind velocities sampled once per hour or more often to obtain the minimal data required to compute an estimate of the wind energy or power functions. These technical expediencies have, in general, resulted in a reduction in the validity, needed precision and accuracy of the data. Even then these systems are still so expensive, complex and require continual maintenance, that only a few of them have ever been employed at any one field site and thus the spatial resolution of the data is also compromised--sometimes to critically much less than is properly required for complete site evaluation by even the most highly skilled engineer or scientist.
Typical prior art wind metering instruments or systems serially measure and record all of the wind characteristic data and do not have a provision for the selection of a low-velocity threshold of measurement, so as to confine their initial point of operation only to the higher "energy winds" of 10-25 miles per hour (mph) velocity, and wind turbine maximum "cut-off" velocities have not been implemented. Mose wind turbine generators do not function efficiently below 10 mph or above 25-30 mph wind velocities, they begin to feather their turbine blades at design velocities and cut-off completely at or below 40 mph. Therefore, metering and recording of these lower or higher wind velocities serves little or no purpose beyond determining the maximum design loads on the blades and supporting structures, which are normally over designed by a large factor for extreme conditions anywhere in the world. Wind direction metering also has little utility since all known wind turbines automatically slew to face the wind, or are insensitive to wind direction as in the case of vertical axis turbines. Consequently, these prior art meteorological wind characteristic metering systems are not efficient in the selection of the kinds and amount of data that they collect and record to only that which is actually needed.
It is also a common prior art practice to utilize the U.S. Weather Bureau or National Weather Service data recorded as peak and average wind velocity values at a few fixed locations throughout the country, to extrapolate an estimate of wind velocities expected at a desired specific site. This data is sufficient for meteorological prediction purposes of the Service but recent experimentation in site evaluation has determined that there is virtually no valid correlation between these extrapolated estimates and the results obtained by actual on-site measurement of the wind velocities. Also, the data can vary by several hundred percent in the average wind speed computations thus obtained due to such wide displacement of the instruments alone, or due to the geographic or topographic differences in adjacent site locations. This has led to expensive errors in the design and the siting of wind turbines which could result in inhibiting the effective use of this important unlimited natural energy resource. Thus, what is now needed are new instruments for the accurate measurement of the wind energy and power production potential at specific sites that are versatile, reliable, inexpensive and can be operated by persons of nominal skill to directly obtain the required data.